This application claims priority from Japanese Patent Application No. 2001-398213 filed Dec. 27, 2001, which is incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to a liquid storing container, an ink jet cartridge, and an ink jet printing apparatus, and more specifically, to a liquid storing container formed of a sheet member in order to store a liquid such as ink supplied to, for example, a pen as a printing section or an ink jet printing head.
2. Description of the Related Art
Containers for storing a liquid have conventionally been known which are based on a method of supplying a liquid while maintaining the interior of the container at negative pressure. With this method, the negative pressure in the container is maintained within an appropriate range for a liquid use section such as a pen point or a printing head which is connected to the container. Thus, while the liquid is not used, it is appropriately prevented from leaking from the liquid use section. Further, when the liquid is used, it is properly supplied in response to a variation in pressure associated with the use.
In the field of ink jet printing, known negative pressure generating mechanisms used inside the container include a sponge as a negative pressure generation source which is stored inside an ink tank as a liquid storing container and a bag-like ink housing section provided with a spring to generate negative pressure by exerting force against inward deformation of the bag resulting from consumption of ink (refer to Japanese Patent Application Laid-open Nos. 56-067269 (1981), 6-226993 (1994), and the like). Another known negative pressure generating mechanism is a conical configuration with a rounded conical portion which is thinner than the peripheral surface of the cone, e.g. the rubber ink storing section disclosed in U.S. Pat. No. 4,509,062.
On the other hand, a method has been known which comprises determining the appropriate range of negative pressure for the liquid use section on the basis of a pressure head difference (a difference in pressure caused by a difference in height between the liquid use section and the container), as opposed to the method of maintaining negative pressure in the container using the above negative pressure generating mechanisms. This method does not require any special mechanisms for the liquid storing section and thus often uses a liquid storing bag formed of a sheet member such as a bag. However, this method requires a specified difference in height between the liquid storing bag and the liquid use section (a printing head or the like). Accordingly, a supply tube or the like is interposed between the liquid storing bag and the liquid use section. This results in a tendency to increase the size of the apparatus.
On the contrary, a liquid storing section provided with any of the above negative pressure generating mechanisms does not require any pressure head differences. This enables the liquid storing container and the liquid use section to be contact with each other. For example, in the field of ink jet printing, a configuration has been known in which an ink tank provided with a negative pressure generating mechanism is integrated with an ink jet printing head. In the specification, such a configuration in which a printing head and an ink tank are integrated together is called an xe2x80x9cink jet cartridgexe2x80x9d. Furthermore, such ink jet cartridges can be roughly classified into configurations in which the printing head and the ink tank are always integrated together and configurations in which the printing head and the ink tank are separate from each other, can each be separated from the apparatus main body, and are integrated together for use.
In any of the above configurations, to allow the efficient use of ink stored in the ink tank, an ink supply port in an ink storing section is provided below the center of the ink tank positioned for use. Correspondingly, the printing head is located below the ink supply port. Thus, the negative pressure generating mechanism must determine the appropriate range of negative pressure for the printing head considering in particular the effects of the gravity on ink. Such negative pressure forms back pressure in connection with the supply of ink to the printing head and makes the pressure in ejection openings in the printing head negative with respect to the atmospheric pressure. This is why it is called xe2x80x9cnegative pressurexe2x80x9d.
One of the most known negative pressure generating mechanisms is the use of capillary force of a porous member. An ink tank configured in this manner has a porous member such as a sponge filled into the entire tank and preferably compressed in it. Further, this configuration is provided with an air communication port. This arrangement prevents an increase in negative pressure in the tank associated with ink consumption, thus allowing ink to be supplied smoothly.
However, it is unavoidable that ink is less efficiently stored in an ink tank using a porous member as a negative pressure generating mechanism, because of the presence of the porous member. To decrease this problem, a known configuration stores ink only in a part of the ink tank instead of inserting it into the entire ink tank. This configuration installs a porous member close to the ink supply port in the ink tank to maintain a predetermined negative pressure to the printing head within an appropriate range. It also directly stores ink on a side further from the ink supply port without using any porous members. This configuration allows ink to be stored more efficiently than the configuration in which the porous member is filled into the entire ink tank. It also allows ink to be supplied appropriately to the printing head.
However, in terms of ink storing efficiency, the use of a porous member as a negative pressure generating mechanism is still insufficient, and the bag-like container composed of a combination of a bag and a spring or the rubber ink tank, described previously, is more excellent.
The known mechanism in which a bag-like ink storing container is provided with a spring to generate negative pressure relates to an ink storing container with a relatively large capacity (for example, 30 cc to 40 cc). Thus, the spring exerts strong force in order to generate negative pressure. Accordingly, a sheet deformed depending on the amount of ink is relatively less rigid. Thus, the rigidity or deformation of the sheet associated with ink consumption does not significantly affect negative pressure generated. That is, it creates no problems in a practical sense though it may make ink supply variable or unstable to some degree.
However, if an ink storing container of a relatively small capacity (for example, less than 30 cc) is formed of a sheet and a spring-based negative pressure generating mechanism is provided, then a new problem may occur particularly owing to a relatively increased sheet rigidity.
For example, if an ink storing container is manufactured by expanding a planar sheet and sticking or welding it to a frame while maintaining its shape, then it is relatively difficult to keep the sticking or welding surface of the sheet flat. Thus, the sheet may wrinkle, or assembly stability or the reliability of sticking may be degraded.
Further, this bag-like ink storing container is a closed system. Accordingly, when only a little ink is left in the container as a result of consumption, the ink may not be used up because of an increase in negative pressure caused by displacement of the sheet or wrinkles formed in the deformed portion. This means that an ink storing container of a small capacity not only stores only a small amount of ink but also provides only a small amount of ink available. This may be a practical problem.
Furthermore, if impact during distribution or a change in environment such as temperature causes a significant change in pressure in the ink storing container, then that change cannot be absorbed by deformation of the sheet. As a result, ink may leak or may be supplied inappropriately.
It is an object of the present invention to provide a liquid storing container, an ink jet cartridge, and an ink jet printing apparatus which can be manufactured reliably, which enable a liquid to be used up appropriately, and in which liquid supply is unlikely to be affected by a change in environment.
In the first aspect of the present invention, there is provided a liquid storing container from which a liquid is supplied to an exterior and in which the liquid is stored, the liquid storing container comprising:
a deformable movable member which form the container and has a portion molded into a convex form;
negative pressure generating means for applying force to the movable member, an applying direction of the force being a direction opposite to a direction in which the movable member is deformed as the liquid is supplied, to maintain the interior of the container at negative pressure with respect to atmosphere; and
an air passage section including an air introduction port in which a liquid meniscus is formed corresponding to pressure relative to the atmosphere and a path having a predetermined length so that the interior of the container communicates with the atmosphere via the path and the air introduction port.
In the second aspect of the present invention, there is provided an ink jet cartridge comprising:
an ink storing container from which ink is supplied to an exterior and in which the ink is stored, the ink storing container including:
a deformable movable member which form the container and has a portion molded into a convex form;
negative pressure generating means for applying force to the movable member, an applying direction of the force being a direction opposite to a direction in which the movable member is deformed as the ink is supplied, to maintain the interior of the container at negative pressure with respect to atmosphere; and
an air passage section including an air introduction port in which an ink meniscus is formed corresponding to pressure relative to the atmosphere and a path having a predetermined length so that the interior of the container communicates with the atmosphere via the path and the air introduction port, and
a printing head ejecting the ink, which is supplied from the ink storing container.
In the third aspect of the present invention, there is provided an ink jet printing apparatus which performs printing by using a printing head to eject ink to a printing medium,
wherein the ink jet printing apparatus uses an ink storing container from which ink is supplied to the printing head and in which the ink is stored, the ink storing container including:
a deformable movable member which form the container and has a portion molded into a convex form;
negative pressure generating means for applying force to the movable member, an applying direction of the force being a direction opposite to a direction in which the movable member is deformed as the ink is supplied, to maintain the interior of the container at negative pressure with respect to atmosphere; and
an air passage section including an air introduction port in which an ink meniscus is formed corresponding to pressure relative to the atmosphere and a path having a predetermined length so that the interior of the container communicates with the atmosphere via the path and the air introduction port.
With the above configuration, the movable member is molded into a convex form, so that even the liquid storing container of a small capacity can maintain a stable capacity. Further, the movable member can exhibit predetermined rigidity. Furthermore, the movable member can remain planar when fixed to, for example, a frame. Therefore, when the movable member is welded or stuck, problems such as wrinkling of their welding or sticking surfaces can be prevented.
Further, the ink storing container is provided with the air passage section in which a meniscus is formed correspondingly to pressure relative to an atmosphere and in which the interior of the liquid storing space is in communication with the atmosphere via the path having a predetermined length. This allows an air to be introduced into the space via the air passage section, when the negative pressure in the storing space increases. On the other hand, when the air in the liquid storing space expands to push the liquid out the storing space, the liquid can be kept in the path.
The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.